If a gas is filled in a rest sphere, its molecules moves randomly due to the heat energy. Will the centre of mass of molecules exist?

If a gas is filled in a rest sphere, its molecules moves randomly due

1.	If a gas is filled in a rest sphere, its molecules moves randomly due to the heat energy. Will the centre of mass of molecules exist?
Answer» Solution :No, there is no any external force EXERTED on a REST sphere and according to the LAW of conservation of MOMENTUM centre of mss of molecules REMAINS rest `therefore vec(v_(cm))=0`